1. Field of the Invention
The invention relates generally to discharge lamps. The invention relates more specifically to novel lamp configurations and to an improved method of manufacturing an electrodeless lamp.
2. Related Art
In general, the present invention relates to the type of lamp disclosed in U.S. Pat. No. 5,404,076, as well as U.S. Pat. No. 5,903,091, each of which is herein incorporated by reference in its entirety.
Electrodeless lamps are known in the art. Such lamps may be characterized according to the type of discharge they produce. Electrodeless discharges may be classified as either E discharges, microwave discharges, travelling wave discharges, or H discharges.
FIG. 1 is a schematic diagram of a conventional electrodeless lamp which produces an E discharge. A power source 1 provides power to a capacitor 2. A gas-filled vessel 3 is placed between the plates of the capacitor 2. E discharges in electrodeless lamps are similar to arc discharges in an electroded lamp, except that current is usually much less in an E discharge. Once breakdown of the gas to its ionized or plasma state is achieved, current flows through the capacitance of the vessels walls between the plates of the capacitor 2, thereby producing a discharge current in the plasma.
FIG. 2 is a schematic diagram of a conventional electrodeless lamp which produces a microwave discharge. A microwave power source 11 provides microwave energy which is directed by a waveguide 12 to a microwave cavity 14 which houses a gas-filled bulb 13. The microwave energy excites the fill in the bulb 13 and produces a plasma discharge. In a microwave discharge, the wavelength of the electromagnetic field is comparable to the dimensions of the exciting structure, and the discharge is excited by both E and H components of the field.
FIG. 3 is a schematic diagram of a conventional electrodeless lamp which produces a travelling wave discharge. A power source 21 provides power to a launcher 22. A gas-filled vessel 23 is disposed in the launcher 22. The gap between the electrodes of the launcher 22 provides an E field which launches a surface wave discharge. The plasma in the vessel 23 is the structure along which the wave is then propagated.
FIG. 4 is a schematic diagram of a conventional electrodeless lamp which produces an H discharge. Electrodeless lamps which produce an H discharge are also referred to as inductively coupled lamps. As shown in FIG. 4, one example for a conventional inductively coupled lamp includes a low frequency power source 31 providing power to a coil 32 which is wound around a gas-filled vessel 33. The alternating current around the coil 32 causes a changing magnetic field, which induces an electric field which drives a current in the plasma. In effect, the plasma can be analyzed as a single turn secondary to the coil 32. An H discharge is characterized by a closed electrical field, which in many examples forms a visible donut-shaped plasma discharge.
A number of parameters characterize highly useful sources of light. These include spectrum, efficiency, brightness, economy, durability (working life), and others. For example, a highly efficient, low wattage light source with a long working life, particularly a light source with high brightness, represents a highly desirable combination of operating features. Electrodeless lamps have the potential to provide a much longer working life than electroded lamps. However, low wattage electrodeless lamps have found only limited commercial applications.